I can think of several reasons they should NOT attempt this but the most reasons I am concerned about is the money that will be taken away from local Uber drivers (which Disney wants).
So many guests at Disney utilize Uber and Lyft due to backed up Disney transportation. In turn, this has actually created a lot of extra income for locals and even a a couple thousand CMs looking to make a little extra cash to supplement their low wages. If Disney decides to do this, those thousands of CMs driving for these services will loose that income. And no, they cannot just be hired by Disney to do the same thing as Disney only allows you to have ONE job with the company.
The real solution is to streamline their own transportation. If that means expanding the monorail, do it. If that means creating an actual People Mover at places like the Boardwalk and Disney Springs area, do it. Expensive? Yes. But they HAVE the money. Adding more and more vehicles on the road (extra busses and possibly this service) is only going to keep delaying the current transportation problem.